Posted May 20, 2013; 01:31 p.m.

by Morgan Kelly, Office of Communications

The potential cancellation of the NASA Kepler satellite mission would mark the end of an unparalleled source of information about planets and planetary systems outside of Earth's solar system, known as exoplanets, according to Princeton University astrophysicistGáspár Bakos, who studies exoplanets and has discovered more than 40.

NASA announced May 15 that a mechanical failure within the Kepler satellite, which launched in 2009 and was extended to run through 2016, means that it can no longer be accurately positioned to make observations. As a result, the space agency may end the data-collection phase of the satellite, though several-years' worth of data remains for scientists to analyze. Scientists have so far used the satellite — which includes a 1 meter-diameter telescope and an extremely high-precision camera — to identify nearly 2,800 planet candidates, of which about 100 have been confirmed.

Bakos can be reached through Princeton science writer Morgan Kelly at 609-258-5729, or mgnkelly@princeton.edu.

Bakos said that although Kepler is popularly known for its mission to discover Earth-like planets, it also has been essential in understanding the characteristics and movement of planets in other solar systems. For example, the satellite has helped scientists establish that small planets are "extremely frequent" in the universe as opposed to the rare hot-Jupiter planets, or planets similar in size and composition to Jupiter but very close to its parent star, he said.

"Kepler has been operating for four years and produced fantastic results," Bakos said. "For example, it found Kepler-62, a five-planet system [1,200 light years from Earth] with planets 1.4 and 1.6 times Earth's radii, and within the parent star's habitable zone." The habitable zone is the optimal distance from a star for a planet to have liquid water and possibly harbor life.

The mechanical failure would scuttle the Kepler mission two years before it was scheduled to end — and there is no other instrument available that can replace it, Bakos said. The next best instrument is the Transiting Exoplanet Survey Satellite (TESS), which was selected by NASA for consideration, but will not fly until 2017 or 2018 at the earliest, said Bakos, who is a co-investigator on that mission. Transiting refers to when a planet passes in front of its star; the resulting light bend indicates to scientists that a planet is present.

In the meantime, scientists would miss out on two years that could increase the chances of discovering extra-small planets as well as extrasolar moons, Bakos said. The moons of exoplanets are especially difficult to detect and none have thus far been discovered.

Bakos joined the Princeton faculty in 2011 and focuses much of his research on extrasolar planets, and on studying the cosmos with small telescopes. Bakos launched and oversees HATNet (Hungarian-made Automated Telescope Network) and HATSouth, planet-hunting networks of fully automated, small-scale telescopes installed on four continents that scan the sky every night for extrasolar planets as they transit in front of their parent star.